1. Field of the Invention
The present invention relates to a method for producing a resin composition containing a fibrous filler.
2. Description of the Related Art
Liquid crystalline polyesters have been used as materials of electric and electronic components and optical components because they are good in molding proccessability, have high heat resistance and strength, and are superior in electric insulation property.
Liquid crystalline polyesters are characteristics in that when molded, molecular chains thereof are easily oriented along the flow direction and therefore anisotropy in mold shrinkage and mechanical properties between the flow direction and the perpendicular direction is easily occur. For this reason, they have been used with incorporation of fillers of various forms such as a fibrous form and a tabular form for reducing anisotropy.
In blending a fibrous filler to a liquid crystalline polyester, the average fiber length of the filler is desired to be controlled in order to obtain desired flowability or moldability and desired strength of molded articles.
In JP-A-6-240114, a flow length in injection molding and a shrinkage of a molded article have been determined by injection molding a pellet prepared from a glass fiber-reinforced liquid crystalline resin composition comprising (A) 100 parts by weight of at least one liquid crystalline resin selected from liquid crystalline polyester resins capable of forming an anisotropic molten phase and liquid crystalline polyesteramide resins and (B) 5 to 300 parts by weight of glass fiber having an average fiber diameter of 3 to 15 μm, wherein the weight average fiber length in the composition pellet is within the range of 0.02 to 0.55 mm, the proportion of glass fiber being larger than 1 mm in fiber length is 0 to 15% by weight of the whole glass fiber, and the proportion of glass fiber being up to 0.1 mm in fiber length is 0 to 50% by weight of the whole glass fiber. This technology, however, is not a technology to control the weight ratio or the average fiber length in filling of glass fiber.
Moreover, the incorporation of a fibrous filler uniformized beforehand in average fiber length makes it possible to control the average fiber length of the filler in the liquid crystalline polyester composition, but it requires classification of the fibrous filler according to fiber length before the incorporation, so that it takes time and cost.